Add permissions to role

Adds one or more permissions to the specified role while preserving existing permission assignments. Use this endpoint to grant additional capabilities to a role without affecting its current permission set. Provide the role name as a path parameter and a list of permission names in the request body. The system will validate that all specified permissions exist in the environment and add them to the role. Existing permission assignments remain unchanged, making this operation safe for incremental permission management. This is useful for gradually expanding role capabilities or adding new permissions as your system evolves. Returns the updated list of all permissions now assigned to the role.